6.5s are typically easier to load for and inherently accurate. Usually takes very little to work loads up. The creedmoor round is the same and the 30 degree shoulder helps he reloaders by reducing stretch thus reducing trimming cases. The shoulder angle improves powder burn efficiency as well.

If you look at energy most rounds in this class are the same out to 400 or so.

The BIGGEST thing is the gun manufacturers did right with the creedmoor by getting the twist correct for heavies.